Add parser for playlist command

src/lib.rs

@@ -9,6 +9,7 @@ pub use structs::{Position, State, Stats, Status, Track, UnitResponse};
 /// some unprintable character to separate repeated keys
 const SEPARATOR: char = '\x02';
 
+/// Parse an interator of string slices into `T`.
 pub fn parse_response<'a, I: Iterator<Item = &'a str>, T: de::DeserializeOwned>(input: I) -> MpdResult<T> {
   let mut map: HashMap<String, String> = HashMap::new();
   for line in input {
@@ -34,19 +35,22 @@ pub fn parse_response<'a, I: Iterator<Item = &'a str>, T: de::DeserializeOwned>(
   Ok(envy::from_iter(map).unwrap())
 }
 
+/// Parse an iterator of string slices into a vector of `T`, splitting at `first_key`.
+/// One possible use for this is the `playlistinfo` command which returns all items in the current
+/// playlist, where the `file: ` key denotes the start of a new item.
 pub fn parse_response_vec<'a, 'b, I: Iterator<Item = &'a str>, T: de::DeserializeOwned>(input: I, first_key: &'b str) -> MpdResult<Vec<T>> {
   input
     .peekable()
     .batching(|it| {
       let mut v = match it.next() {
-        // if the playlist is empty or we’ve reached the end,
-        // the response is only the `OK` line.
+        // if the response is empty or we’ve reached the end,
+        // we receive only the `OK` line.
         Some("OK") => return None,
         // otherwise this is the file attribute and thus the first key-value of this track
         Some(s) => vec![s],
         _ => return None,
       };
-      // Only peek here in case we encounter the `file:` line which we still need for the next track.
+      // Only peek here in case we encounter the first key (e.g. `file:`) line which we still need for the next track.
       while let Some(l) = it.peek() {
         if l.starts_with(first_key) {
           return Some(v);
@@ -62,6 +66,21 @@ pub fn parse_response_vec<'a, 'b, I: Iterator<Item = &'a str>, T: de::Deserializ
     .collect()
 }
 
+/// Parse the `playlist` command, a list of key-value pairs, as a vector of filenames.
+/// The playlist index of each item is *not* included because, if needed,
+/// it can easily be added with `.enumerate()`.
+pub fn parse_playlist<'a, I: Iterator<Item = &'a str>>(input: I) -> MpdResult<Vec<&'a str>> {
+  input
+    // `iter.scan((), |(), item| predicate(item))` is equivalent to map_while(predicate),
+    // but the latter isn’t stabilized (yet).
+    .scan((), |(), s| match s.splitn(2, ' ').next_tuple() {
+      Some(("OK", _)) | None => None, // Covers OK with message and without
+      Some(("ACK", err)) => Some(Err(Error::from_str(err))),
+      Some((_, filename)) => Some(Ok(filename)),
+    })
+    .collect()
+}
+
 #[cfg(test)]
 mod tests {
   use super::*;
@@ -96,7 +115,7 @@ OK";
         title: Some("American Pie".to_string()),
         track: Some(Position {
           item_position: 1,
-          total_items:   None,
+          total_items: None,
         }),
         duration: Some(Duration::from_secs_f64(512.380)),
         pos: 1367,
@@ -152,11 +171,11 @@ OK"#;
         title: Some("Symphonie No. 41 en ut majeur, K. 551 \"Jupiter\": I. Allegro Vivace".to_string()),
         disc: Some(Position {
           item_position: 1,
-          total_items:   Some(1),
+          total_items: Some(1),
         }),
         track: Some(Position {
           item_position: 6,
-          total_items:   Some(6),
+          total_items: Some(6),
         }),
         duration: Some(Duration::from_secs_f64(682.840)),
         pos: 3439,
@@ -215,7 +234,7 @@ OK";
     );
   }
   #[test]
-  fn de_playlist_test() {
+  fn de_playlistinfo_test() {
     let input_str = "file: 137 A New World.mp3
 Last-Modified: 2018-03-07T13:11:43Z
 Artist: Arata Iiyoshi
@@ -294,13 +313,13 @@ OK";
     assert_eq!(
       s,
       Stats {
-        uptime:      Duration::from_secs(23691),
-        playtime:    Duration::from_secs(11288),
-        artists:     2841,
-        albums:      2455,
-        songs:       40322,
+        uptime: Duration::from_secs(23691),
+        playtime: Duration::from_secs(11288),
+        artists: 2841,
+        albums: 2455,
+        songs: 40322,
         db_playtime: Duration::from_secs(11620284),
-        db_update:   1588433046,
+        db_update: 1588433046,
       }
     );
   }
@@ -318,4 +337,29 @@ OK";
       Err(error::Error::from_str(r#"[2@0] {consume} wrong number of arguments for "consume""#))
     );
   }
+
+  #[test]
+  fn parse_playlist_test() {
+    let input = "0:file: Brent Barkman & Maribeth Solomon/Sunless Sea (2015)/01 Opening Screen.flac
+1:file: Brent Barkman & Maribeth Solomon/Sunless Sea (2015)/02 Wolfstack Lights.flac
+2:file: Brent Barkman & Maribeth Solomon/Sunless Sea (2015)/03 Submergio Viol.flac
+3:file: Brent Barkman & Maribeth Solomon/Sunless Sea (2015)/08 Dark Sailing.flac
+4:file: Brent Barkman & Maribeth Solomon/Sunless Sea (2015)/17 The Sea Does Not Forgive.flac
+5:file: Brent Barkman & Maribeth Solomon/Sunless Sea (2015)/18 Hope Is an Anchor.flac";
+
+    match parse_playlist(input.lines()) {
+      Err(_) => panic!("Should not be an error"),
+      Ok(tracks) => assert_eq!(
+        tracks,
+        vec![
+          "Brent Barkman & Maribeth Solomon/Sunless Sea (2015)/01 Opening Screen.flac",
+          "Brent Barkman & Maribeth Solomon/Sunless Sea (2015)/02 Wolfstack Lights.flac",
+          "Brent Barkman & Maribeth Solomon/Sunless Sea (2015)/03 Submergio Viol.flac",
+          "Brent Barkman & Maribeth Solomon/Sunless Sea (2015)/08 Dark Sailing.flac",
+          "Brent Barkman & Maribeth Solomon/Sunless Sea (2015)/17 The Sea Does Not Forgive.flac",
+          "Brent Barkman & Maribeth Solomon/Sunless Sea (2015)/18 Hope Is an Anchor.flac",
+        ]
+      ),
+    }
+  }
 }